package com.shujia.process_contr;

import javax.swing.*;
import java.util.Scanner;

public class SwitchExer1 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int score = sc.nextInt();
        if (0 <= score && score <= 100) {
            score /= 10;
            switch (score) {
                case 10:
                case 9:
                    if (true) {
                        System.out.println("A");
                        break;
                    }
                case 7:
                case 8:
                    System.out.println("B");
                    break;
                case 6:
                    System.out.println("C");
                    break;
                default:
                    System.out.println("D");
            }
        } else {
            System.out.println("成绩不合法!");
        }


    }
}
